Mercedes-AMG GT S v Porsche 911 GT3 v Audi R8 LMX comparison review

In front of me are three choices. Each looks very tempting in its own unique way, but just like Goldilocks I need to experience my three choices before I can declare which one is just right.

But I'm not picking the best porridge or most comfortable chair. No, I've got to find the best new two-seat sports car from three of the ultimate choices.

First up it's the all-new Mercedes-AMG GT S, the much-hyped replacement for the SLS 'gullwing'. The car the folks at parent company Daimler hope pushes the AMG brand up a notch, from hot rod tuning division to outright sports car rival to the likes of Porsche.

Speaking of the cars from Stuttgart, next up is the ultimate road-going racer the 911 GT3. The 911 may be the benchmark sports car but that doesn't stop the engineers at Porsche turning it up to 11 to create the racetrack-ready GT3.

And last, but certainly by no means the least, is the Audi R8 LMX. It's the final iteration of the Ingolstadt brand's first genuine supercar before the new model arrives in 2016.

So which of these three is the best sports car money can buy? We've taken all three to Melbourne's Sandown Raceway to put them to the test at the limit.

Goldilocks didn't have this much fun picking her porridge.

Mercedes-AMG GT S

There's a lot riding on the broad haunches of the new GT. Its predecessor, the SLS, was a good car and thanks to its funky doors it will be remembered as a theatrical masterpiece. But it wasn't flawless.

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And, as the name suggests, Mercedes wants AMG to become synonymous with sports cars as well as its maniacally brilliant re-workings of Mercedes' passenger car line-up.

Under the bonnet, sitting behind the front axle, which technically speaking makes it a front-mid engine layout, is AMG's new 4.0-litre twin-turbo V8 engine that replaces the SLS's 6.2-litre naturally aspirated V8.

Producing 375kW of power and 650Nm of torque it doesn't out gun the old SLS figures of 420kW and 650Nm. But it is hardly underpowered and manages to use significantly less fuel; a claimed 9.4-litres per 100km on the combined cycle compared to 13.3L/100km the SLS consumed. The engine sends its grunt to the rear wheels via a seven-speed dual-clutch transmission.

But what the facts and figures don't tell you is if the new engine can live up the old V8's epic soundtrack and beautifully linear power delivery. The good news is it manages to do both.

The new turbocharged engine growls and roars just like the old bent eight and despite the forced induction the power comes on with no obvious lag. In fact, the power comes on some quickly you need to be judicial with your right foot when accelerating out of corners, because breaking traction is not difficult.

By fitting the engine behind the front axle, AMG has managed to make the GT a genuine sports car when it comes to handling. The GT feels agile, responsive and direct on the track thanks to super quick steering, well sorted suspension and grippy Michelin tyres.

The steering is so quick it takes a minute to recalibrate your senses but once you do it is so accurate you can place the GT exactly where you want it. The only criticism is the weighting is a touch light by sports car standards.

Braking performance is phenomenal with excellent initial bite and strong pulling power despite numerous laps. But it should be because our test car was fitted with AMG's ceramic braking package which costs an additional $17,500.

Our test car was also fitted with the $19,000 Edition 1 package which includes a more aerodynamic bodykit that adds a new bumper and fixed rear wing.

The rest of the GT cabin is a blend of performance and luxury. The quality is top-notch and makes it the stand-out in the group for refinement.

Mercedes-AMG GT S price and specifications

Price: $295,000 plus on-road costs

On sale: Now

Engine: 4.0-litre twin turbo V8 petrol

Power: 375kW at 6250rpm

Torque: 650Nm at 1750rpm

Transmission: Seven-speed dual-clutch automatic, RWD

Fuel use: 9.4L/100km

Porsche 911 GT3

When it comes to sports cars few can match the success and longevity of the 911. It truly is the benchmark for performance cars and the GT3 is the 911 at its most dynamic; loaded with lessons learned on the racetrack-ready 911 GT3 and Carrera Cup racers.

The 911 Turbo is more powerful and available with all-wheel drive but the GT3 is the 911 you buy if driving enjoyment and engagement is your priority.

Under the rear bonnet is a 3.8-litre six-cylinder boxer engine that produces 350kW of power and 440Nm of torque. Without the aid of turbochargers the Porsche needs lots of revs to reach those peak figures – 8250rpm and 6250rpm respectively – but it has plenty of punch right across the rev range.

And it also makes a brilliant noise in the process. The unmistakable flat-six Porsche soundtrack is amplified in the GT3, especially as you take it towards past 6500rpm, where the noise becomes a scream.

The downside of extracting so much performance from a naturally-aspirated engine is higher fuel consumption. The GT3 uses 12.4L/100km, well behind the AMG and only marginally ahead of the R8.

For the first time in the history of the GT3 the engine is not paired with a manual transmission. Instead the engine sends its power to the rear wheels via Porsche's seven-speed dual-clutch gearbox (PDK).

The main reason for the switch is simple – the PDK is faster than a manual. It has been specifically tuned for the GT3 with two shift modes, Normal and Sport, with a button on the console to switch between the two.

Sport mode has been tuned for racetrack use so gears are held for longer and gear changes at higher revs. But if you want control you can switch into manual mode and use the shift paddles behind the steering wheel.

On the track the GT3 is in its element. The chassis is so well balanced it can carry so much corner speed it is more likely the driver will run out of ability rather than the car. The steering is almost telepathic, perfectly weighted and very direct. It is helped by a new active rear-wheel steering set-up that is able to turn the rear wheels by up to 1.5 degrees when cornering.

The GT3 also gets Porsche's Torque Vectoring Plus system to supplement the rear steering, which is able to direct more power to the outside rear wheel for even sharper turning.

Braking power is equally matched to the rest of the car's performance despite missing out on ceramic brakes. The 911's aluminium discs, grabbed by six-piston calipers, felt just as strong under deceleration as the other two, with excellent pedal feel, plenty of bite and no signs of fade.

The interior continues the racing theme with a functional, rather than luxurious, layout; in other words, there is more fake suede rather than leather.

Our test car was fitted with six-point racing harnesses, a fire extinguisher and a rollcage where the rear seats should be as part of the Club Sport package which can be added at no extra cost for those who plan on plenty of track days.

But this focus on lightweight performance comes at the cost of items like a reversing camera – which is standard on the other two cars here – which slightly blunts its value argument.

Porsche 911 GT3 price and specifications

Price: $293,600 plus on-road costs

On sale: Now

Engine: 3.8-litre six-cylinder petrol

Power: 350kW at 8250rpm

Torque: 440Nm at 6250rpm

Transmission: Seven-speed dual-clutch automatic, RWD

Fuel use: 12.4L/100km

Audi R8 LMX

It is better to go out with a bang rather than a whimper – or so the old saying goes.

That appears to have been the mission statement behind the R8 LMX. It may be the final version of the four-ringed brand's thoroughbred sports car but it is the best.

More powerful, faster and the first production car in Australia with laser headlights, the LMX has raised the bar for the second generation R8.

The engine is the same mid-mounted 5.2-litre V10 found in the R8 V10 Plus (and Lamborghini Gallardo) but Audi has managed to extract even more performance. Power is 419kW, a 15kW bump on the V10 Plus, but torque remains the same, at 540Nm. The engine is mated to a seven-speed dual-clutch automatic transmission and sends power to the road via Audi's quattro all-wheel drive system.

The drivetrain combines to give the R8 beautiful balance on the track and the all-wheel drive means it has little trouble getting its considerable power transmitted to the tarmac. In the damp conditions we faced on the day it was significantly easier to drive than both the AMG and Porsche.

The engine is the highlight of the car, pulling strongly right across the rev range and making a glorious V10 scream. Its power advantage was evident at the end of Sandown's back straight, hitting the highest speed of this trio; more than 5km/h quicker than the other two on average.

The switch to a dual-clutch gearbox (from the previous single-clutch robotized manual) has made the R8 a much sharper machine, with smoother shifts that are even faster.

The mid-engine layout means sharp and predictable handling. In combination with the all-wheel drive it made the R8 the easiest of the trio to extract maximum performance out of.

But where the R8 falls short of its rivals is inside. The cabin is where the age of the Audi is evident, with a design that looks dated. The materials are still high quality but the low-res digital display on the dashboard isn't befitting at car of this price.

Which is the other big drawback for the R8 LMX – value. At $440,000 it is not only significantly more expensive than the AMG and Porsche but also more expensive than the new Lamborghini Huracan and pushes Audi into the same price territory as Ferrari.

But this is one of only three LMX's that have made it to Australia so it does come with greater exclusivity than its Italian rivals.

Audi R8 LMX price and specifications

Price: $440,000 plus on-road costs

On sale: Now

Engine: 5.2-litre V10 petrol

Power: 419kW at 8000rpm

Torque: 540Nm at 6500rpm

Transmission: Seven-speed dual-clutch automatic, AWD

Fuel use: 12.9L/100km

Verdict

In this contest there are no losers, but two cars can't win.

In Goldilocks terms it is the R8 LMX that drops out of the reckoning first, being too expensive and too old. The new R8 arrives in 2016 and promises to be a step forward in both performance and presentation, and just as importantly will cost less.

Even at the end of its life, the R8 remains a genuine supercar from a mainstream luxury brand. It has the performance to match it with the AMG and the Porsche thanks to the sweet V10 and clever all-wheel drive system.

Splitting the GT and the GT3 is more difficult, primarily because they offer two different interpretations of the sports car concept.

The AMG blurs the lines between a grand tourer and a genuine sports car, offering speed and thrills as well as being a comfortable, luxurious and liveable car with plenty of character. The Porsche, though, is a sharper, more focussed tool. It is as pure and focused as a sports car can be and rewards good driving with a level of engagement and enjoyment that very few cars can match.

The AMG GT is undoubtedly the best fit for Goldilocks, but for those with a hotter palette the Porsche is still the tastier track weapon on the table.